I have just migrated my local Drupal development platform from an old machine with Mac OS X Mountain Lion to a brand new (and most lovely) MacBook Pro with Mac OS X Yosemite and discovered that the default version of PHP5 (and Apache2) for Mac OS X Yosemite 10.10.1 does not have the GD graphics manipulation libraries installed (the gd.so is missing).

Given that the default Apple versions are not easily extended, it is worth installing separate PHP5 and Apache2 under package control, for which I used MacPorts (one could also use Homebrew). I have a step-by-step guide here:

Mac OS X Yosemite: how to install (non-Apple) PHP5 and Apache2 HTTP Server for Drupal with MacPorts, including GD graphics support

Comments are not accepted on that site, relevant replies w.r.t. the guide are welcome here.